1. Field of the Invention
The present invention relates to a drive control system for a battery car (electric automobile car) which can reduce burden on the driver at start and slow speed drive of the battery car, in particular on a sloping road.
2. Description of the Prior Art
In general, there are various types for driving a battery car, for instance such as to transmit a motor drive power directly to driving wheels via a reduction gear by making the best use of flat torque characteristics of a motor, or to mount a clutch and a manual transmission so that the battery car can be driven in the same way as a gasoline engine car. In conventional battery cars, however, fine or delicate accelerator pedal operation is particularly required from a start to a slow speed drive during which motor output torque is small, so that a burden has been cast upon the driver.
To overcome this problem, various methods have been so far proposed as follows: Japanese Laid-Open Patent Publication No. 62-217804 discloses such a technique that a forward/backward command signal for switching the vehicle drive direction from the forward to the backward or vice versa is inputted to a control unit as a motor directional signal indicative of the motor rotating direction whenever the number of revolution of the motor reaches zero, so that the motor starting operation can be smoothed.
Further, Japanese Laid-Open Utility Model Publication No. 1-86401 discloses a method wherein whenever the battery car is started, a current limit value (roughly proportional to the maximum torque) of the driving motor is increased to facilitate the start of the battery car.
Further, Japanese Laid-Open Patent Publication No. 3-253202 discloses such a technique that whenever the vehicle speed is reduced down roughly to zero, current of a predetermined rate is supplied from the battery to the driving motor to generate a small driving power for driving the driving wheel slightly so that both the repetitive accelerator and brake pedal depression can be omitted whenever the battery car is driven at slow speed in a traffic jam.
In the above-mentioned prior art methods, however, in the case of the battery car having no automatic transmission provided with a torque converter, there exists a problem in that the battery car is caused to move down due to deficiency of accelerator pedal depression or is started abruptly due to the reaction thereof when the battery car is started on a sloping road. Further, even in the case of a battery car having an automatic transmission provided with a torque converter, the battery car cannot perfectly follow the load fluctuations due to change in road gradient. On the other hand, there exists another problem in that the cost of the battery car inevitably increases.